长期耕作对农田黑土几丁质降解菌群及酶活性的影响

Effects of Long-term Different Tillage Practices on Chitin Degrading Microbial Communities and Chitinase Activity in Farmland Black Soil

为揭示长期耕作对农田黑土几丁质降解菌群及酶活性的影响及其驱动因子,以黑土区耕法长期定位试验为平台,采用荧光定量和高通量测序技术研究不同耕作措施(灭茬起垄、免耕、间隔深松和翻耕)下0~40cm土层chiA几丁质降解菌基因丰度、微生物群落结构和酶活性。结果表明:0~20 cm土层,免耕显著提高chiA基因丰度;20~40 cm土层,免耕降低chiA基因丰度、alpha多样性和变形菌门(Proteobacteria)相对丰度,但是增加放线菌门(Actinobacteria)相对丰度。土壤pH、平均重量直径和养分含量显著影响chiA基因丰度和群落结构。与灭茬起垄相比,免耕显著提高0~20 cm土层几丁质酶活性,而间隔深松和深翻显著提高0~40 cm土层几丁质酶活性。结构方程模型模拟发现耕作方式、土壤深度、平均重量直径、土壤有机碳、全氮、全磷、chiA基因丰度和放线菌门相对丰度对几丁质酶活性具有显著直接效应。研究结果为明确黑土区不同耕作措施对土壤几丁质降解的影响提供理论基础。

【Objective】This study aimed to illustrate the impacts of different tillage practices on chitin degrading microbial communities and chitinase activity in farmland black soil,and to explore the main environmental factors in driving a change in chitin degrading microbial communities and chitinase activity.【Method】Based on the long-term positioning platform of different tillage practices in black soil and the combination of fluorescence quantification and high throughput sequencing technology,this research intends to study the effects of long-term different tillage practices(Conventional tillage,No-tillage,Sub-soiling tillage,Moldboard plowing tillage)on chitin degrading bacteria harboring chiA gene abundance,microbial communities and chitinase activity in 0–40 cm soil layers.【Result】Results showed that no-tillage increased chiA gene abundance in the 0–20 cm soil layer.Lower chiA gene abundance,alpha diversity and proteobacteria relative abundance,and higher actinobacteria relative abundance in the 20–40 cm soil layer of no-tillage than other tillage practices.The abundance of chiA gene and microbial community structure was significantly affected by soil pH,mean weight diameter and nutrients.Compared with conventional tillage,the chitinase activity increased in 0–20 cm soil layer under no-tillage,and the chitinase activity was enhanced in 0–40 cm soil layer under sub-soiling tillage and moldboard plowing tillage.The simulation result of the structural equation modeling showed that chitinase activity was directly affected by the tillage practice,soil depth,mean weight diameter,organic carbon,total nitrogen,total phosphorus,chiA gene abundance,and actinobacteria relative abundance.【Conclusion】These results provide a theoretical basis for understanding the effect of different tillage practices on soil chitin degradation in black soil areas.